netdev - Re: [devel-ipsec] [PATCH ipsec-next, v2] xfrm: support sending NAT keepalives in ESP in UDP states

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Date: Sun, 10 Dec 2023 11:14:25 -0800
From: Eyal Birger <eyal.birger@...il.com>
To: Michael Richardson <mcr@...delman.ca>
Cc: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	kuba@...nel.org, pabeni@...hat.com, steffen.klassert@...unet.com, 
	herbert@...dor.apana.org.au, pablo@...filter.org, paul@...ats.ca, 
	nharold@...gle.com, devel@...ux-ipsec.org, netdev@...r.kernel.org
Subject: Re: [devel-ipsec] [PATCH ipsec-next, v2] xfrm: support sending NAT
 keepalives in ESP in UDP states

Hi Michael,

On Sun, Dec 10, 2023 at 10:47 AM Michael Richardson <mcr@...delman.ca> wrote:
>
>
> +               BUILD_BUG_ON(XFRMA_MAX != XFRMA_NAT_KEEPALIVE_INTERVAL);
>
> This code was there before, and you are just updating it, but I gotta wonder
> about it.  It feels very not-DRY.
> It seems to be testing that XFRMA_MAX was updated correctly in the header
> file, and I guess I'm dubious about where it is being done.
>
> I said last year at the workshop that I'd start a tree on documentation for
> XFRM stuff, and I've managed to actually start that, and I'll attempt to use
> this new addition as template.

I'd definitely appreciate any documentation merged into the code.

>
> As a general comment, until this work is RCU'ed I'm wondering how it will
> perform on systems with thousands of SAs. As you say: this is a place for
> improvement.  If no keepalives are set, does the code need to walk the xfrm
> states at all.  I wonder if that might mitigate the situation for bigger
> systems that have not yet adapted.  I don't see a way to not include this
> code.

The work isn't scheduled unless there are states with a defined
interval, so afaict this shouldn't affect systems not using this
feature. Or maybe I didn't understand your point?

Thanks,
Eyal.